Six years ago Canadian scientists reported that sea gulls living near steel mills on the Great Lakes passed genetic mutations to their offspring at a much higher rate than did gulls in rural areas. The source of the mutations was not known at the time, but the prime suspect was air pollution because the gulls nearest the steel mills had the most mutations.

The researchers now report, in a study of mice, that air pollution almost certainly caused genetic mutations in animals and these mutations were inherited by the next generation. The mice with the mutations breathed air near a major highway and two steel mills in Ontario.

It is not yet known what effects, if any, the mutations have on the health of the mice, and more research needs to be done before the findings can be extended to humans.

Still, the new findings suggest that genetic changes caused by pollution can be inherited. The researchers report today in Science that the mutations were caused by airborne particles in emissions from steel plants or automobiles.

“This is a remarkable and interesting observation, and it raises new concerns about the consequences of exposure to airborne pollutants,” says Jonathan Samet of Johns Hopkins University in Baltimore, who wrote an accompanying commentary.

Mice lived for ten weeks in this shed, located downwind of two steel mills.Image courtesy Science.

In the study, James Quinn of McMaster University in Hamilton, Ontario, and his colleagues studied two groups of mice in sheds near Hamilton Harbor, an industrial hub also known as Steel Town. One group of mice breathed polluted air, while the other breathed filtered air—everything else in their environments was the same.

After ten weeks, the researchers bred both groups of mice and looked for mutations in the DNA of offspring. Baby mice in the “unfiltered” group inherited twice as many mutations as mice in the “filtered” group.

Next, the researchers traced the sources of the mutations in the offspring and found that most had come from the fathers. The researchers speculate that sperm is being generated constantly and may be more sensitive than eggs to DNA damage caused by air pollution.

A self-described environmental biologist, Quinn has investigated the effects of pollution on generations of animals in Hamilton Harbor for a decade, first on gulls and then on mice.

“I can assure you that if I lived in Hamilton Harbor I would install a filtration unit in my home or wear a mask when I went out,” he says.